1. Field of the Invention
The present invention relates to an improvement of an energy converter for transferring thermal energy from a low heat source to a high heat source with the use of a mixed medium, for increasing performance of transferring thermal energy of the above energy converter, improving performance of an evaporator and a condenser, and reducing production costs of the converter. Moreover, the present invention improves the performance over a wide range even with partial loads, and provides a highly efficient and multi-functional energy converter having a function as a thermal power generator.
2. Description of the Related Art
In heat pumps and refrigerators of this kind for transferring thermal energy from a low heat source to a high heat source, hitherto, use has essentially been made of (1) compression-type devices with the use of a single component medium such as flon, ammonia and the like or an azeotropic mixed medium prepared by mixing various refrigerant carriers having the same boiling point (reverse Rankine cycle), (2) for the purpose of improving high performance for reverse Rankine cycles, compression-type devices with the use of a non-azeotropic mixed medium prepared by mixing various refrigerant carriers having different boiling points (Lorentz cycle), or (3) absorption-type devices (absorption cycle) combining a refrigerant carrier with an absorbent, such as ammonia with water, water with lithium bromide (LiBr) and the like.
In the known compression-type heat pumps and refrigerators for carrying out reverse Rankine cycles, improvement of a coefficient of performance is limited, particularly, when a temperature change of a heat source is large, a coefficient of performance becomes small. In order to eliminate this shortcoming, there have been developed compression-type heat pumps and refrigerators of Lorentz cycle that use of a non-azeotropic mixed medium prepared by mixing various refrigerant carriers having different boiling points. The compression-type heat pump and refrigerant of this cycle is based on the idea that a temperature changes when a medium phase-changes in an evaporator and a condenser, so that the temperature change with a heat source is matched, thereby increasing effective energy in the evaporator and the condenser, and reducing power of the compressor so as to largely increase a coefficient of performance.
However, the use of a non-azeotropic mixed medium disadvantageously lowers heat transfer efficiency in the evaporator and condenser, increases condensation pressure, lowers evaporation pressure and increases the power of the condenser. The lowering of this heat transfer efficiency particularly obviously occurs at the outlet of the condenser. This is because an easily condensable high boiling point medium is first condensed in the condenser, and a hardly condensable low boiling point medium is left at the outlet of the condenser. Therefore, there is known a method of dividing a condenser into multiple stages, separating a medium into a condensate condensed at each stage and vapor not condensed at each stage, condensing only the non-condensed vapor at a heat source again, and repeating these steps. However, even in this case, concentration of a low boiling point medium is gradually increased in the non-condensed vapor, and if complete condensation of the vapor is attempted at the heat source of a certain temperature, condensation pressure is forced to become high. Therefore, it is disadvantageous that power of the compressor cannot sufficiently be lowered, and the same also happens in the evaporator.
In an absorption-type heat pump and refrigerator, a coefficient of performance becomes small as compared with the above compression-type device. In this connection, there have been studied and developed multiple-effect absorption cycles, GAX (Generator-Absorber-Heat Exchanger Cycle) for reducing heating capacity of a regenerator by using part of the exhaust heat of an absorber for heating the regenerator, triple cycles and the like, but a higher coefficient of performance than that of the above compression-type device cannot be obtained.
There has been further studied and developed compression-absorption-type hybrid device combining a compression-type devices with an absorption-type device, but there remains the above point, that is, a problem of the lowering performance of the condenser and evaporator when using a mixed medium, and there is no expectation for high performance and compactness of the apparatus.
On the other hand, partial load in the known heat pump and refrigerator is controlled by controlling the circulating amount of a working medium, and further controlling the composition when using a mixed medium. However, big problems including the lowering of performance due to changes of circulating amount, difficult composition control, enlarged apparatus and the like.